Lecture 18

Question 1

What are biodiversity hotspots and how many terrestrial ones are there?

Answer 1

25 terrestrial ones.
These are the areas where endemic species are going extinct and there are high levels of habitat loss. These are the areas which we need to focus on if we want to preserve biodiversity

Question 2

Describe the early spread of mammals

Answer 2

Changes in worldwide fauna during Triassic (250-210mya)
. Mammal-like reptiles and reptiles disappeared mid-late Triassic
. Radiation of archosaurs
. Replaced late Triassic by dinosaurs, widespread
. First mammals egg laying, (monotremes) in Triassic e.g. the platypus
. Modern mammals (placentals, marsupials) late Cretaceous (~100 mya). Marsupials only successful in S Hemisphere (evolved there)

Question 3

Why does Australia (and S America, but not to the same extent) have so much endemicity?

Answer 3

Because Australia and S America were isolated from other land masses in Miocene

Question 4

What are angiosperms?

Answer 4

Flowering plants spread all over the world before the complete breakup of Pangea

Question 5

Explain the origin of flowering plants and what has happened since their origin (when, how they spread, their evolution in relation to first vascular plants)

Answer 5

. They dominate world flora today 300-400 families, up to 300,000 species (10,000 species pteridophytes- ferns. 759 species gymnosperms- conifers)
. Origin in paleotropics, 135mya, radiated worldwide in <10mya
. 300my after first vascular plants (so evolved late)

Question 6

What is Amborella? Where’s it found?

Answer 6

Is thought to be the missing link in the evolution of flowering plants. It is thought to be one of the earlier ones, lacks vessels in xylem. It is found in wet forests, New Caledonia

Question 7

When does molecular DNA evidence from mitochondrial, nuclear and chloroplast genomes suggest the split between gymnosperms and angiosperms was?

Answer 7

Late Carboniferous ~290 mya (but they didn’t diversify until about 135mya- the peak/ when they took over)

Question 8

Why do we miss most of the fossil evidence for the evolution of flowering plants?

Answer 8

They were probably restricted to dry uplands and things don’t fossilise well in dry uplands

Question 9

What were the advantages of angiosperms when they evolved?

Answer 9

. Tough leathery leaves, smaller so more drought resistant
. Resistant seed coat prevents desiccation
. More efficient water conducting vessels
. Rapid life history, rapid reproduction an advantage in disturbed environmental conditions or
. Accelerated speciation rates led to diversity of adaptive types

Question 10

How was the environment changing when angiosperms emerged?

Answer 10

CO2 levels and temperatures were increasing.
~140mya Oceanic anoxia sea floor spreading.
Continents of Africa, S America formed, India, Australia and Antarctica distinguishable. Volcanic activity- elevated CO2 (think this was down to volcanic activity). So, changed in global sea levels and atmosphere from ‘superplume’ episode

Question 11

Why was there such rapid diversification of angiosperms?

Answer 11

Insect-angiosperm co-evolution

Question 12

Why is insect pollination advantageous to the first flowering plants?

Answer 12

Genetic exchange between widely spaced individuals, small populations. If you have small populations and high levels of gene flow between them, you can count a random drift. So, there was regular genetic exchange between widely spread individuals and small populations counting on genetic drift

Question 13

What are cosmopolitan taxa? Give examples. Why aren’t there that many species?

Answer 13

. Species found all/ most regions of the world
. Few truly cosmopolitan (humans)
. Several migrated with humans e.g. house sparrow, plantain
. Few species have the physiology/ behaviour that permit survival over entire range of Earth climates
. Many higher taxonomic ranks (genera, families) are cosmopolitan (there aren’t that many cosmopolitan species but there are lots of cosmopolitan groups, genera, families) e.g. insects, grasses

Question 14

What is widespread taxa? give examples

Answer 14

Common in only suitable habitats in well-defined regions of the world. Species that define a particular climate. E.g.
. Penguins- cold, lower latitudes
. Heather- West, Oceanic Europe
. Pine- Boreal climates
. Cacti- dry regions of N, central and S America

Question 15

What are the three groups of mammals?

Answer 15

. Egg layers
. Placentals (on most continents)
. Marsupials

Question 16

Where are marsupials found? What is their distribution explained by?

Answer 16

Australia, S America and 2 species in N America.
Explained by continental drift. S America and Australia were connected by Antarctica, so it is thought that they migrated through Antarctica (you get quite a few marsupial fossils found in Antarctica)

Question 17

Why do mammals have disjunct distribution/ are scattered?

Answer 17

Large migration barriers between locations

Question 18

What are endemic species?

Answer 18

(Many species of higher taxonomic ranks endemic)

Found only in one well-defined region, large or small.

Question 19

Why does conservation tend to focus on endemic species? Give examples of some endemic species

Answer 19

Because if they are lost from that region then they are lost for good.
. Finches on individual islands of Galapagos
. Red Grouse- Britain
. Rosy periwinkle- Madagascar
. Eucalyptus- Australia

Question 20

There are more shared plant families across different world regions than in mammals/ higher similarities of plants between the continents. Why is this?

Answer 20

. Plants evolved earlier when continents were still close together
. Plants disperse more easily
. Mammals are more prone to going extinct (more extinction events)

Question 21

Give the example of the evolutionary relict Magnolias

Answer 21

The distribution is thought to have happened because of the last million years with periodic glaciations. It is thought that with the constant glaciation the more competitive species outcompeted them but that they used to spread all the way across

Question 22

Give 2 examples of climatic relicts

Answer 22

. Arctic springtail

. Gorillas

Question 23

Plants have better dispersal and migration than animals have. Why is dispersal and migration important?

Answer 23

. Successful species multiply and spread
. Genetic isolation increases speciation
Migration and dispersal play key roles in controlling patterns of diversity

Question 24

What is it called when both sexes are on the same plant?

Answer 24

Monoecious

Question 25

What are the potential issues of animal dispersal? (for the animal and people)

Answer 25

1. Mobile- potentially rapid migration (e.g. rabbits in Australia, 1788- plague no.s by 1890. Starling from New York to Canada in 50y- collared Dover- dispersed through Europe)
2. Disadvantage- most animals need 2 individuals of opposite sex to breed
3. Food source- many insects (especially moths) monophagous/ specialists- single food source (so if not there when it lands then it can’t survive). Vegetation structure
4. May carry parasites and diseases- which can move to new areas as well

Question 26

Migration is most rapid when there is continuity of habitat (no breaks in it). Give the types of breaks

Answer 26

1. Corridors
2. Barriers
3. Filters
4. Bridges

Question 27

What are corridors, talking about migration?

Answer 27

Stretches continuous habitat, land or water, allow migration in both directions.

Question 28

What are barriers, talking about migration? Include examples

Answer 28

Patches of unfavourable habitat e.g. Oceans, English Channel. Rarely prevent migration entirely- alter rare and act selectively. Don’t always remain constant e.g. Caribbean Islands, have moved quite considerably over the last 130my. 130mya sterile, drifted to N America 80 mya then drifted east. Allow some migration between north and south

Question 29

What are filters, talking about migration? Give an example

Answer 29

Selective corridors- only allow species with certain characteristics through them e.g. Pyrenees, allow cold tolerant species to disperse/ migrate

Question 30

What are bridges, talking about migration? Give an example

Answer 30

Temporary corridors e.g. Beringia. Allowed passage between Asia and N America (Alaska and Russia) for cold tolerant species. The sea is only 50m deep so, changes in sea levels can expose areas of habitat that animals can migrate on. Controlled development of diversity on both continents